Large aircraft, such as for example commercial or transport aircraft, comprise on each of their supporting surfaces a plurality of similar flaps which act in a similar manner and which are to be driven synchronously. Such flaps are, for example, the landing flaps arranged on the rear edge of the supporting surface. Said landing flaps are generally divided into inner, outer and central landing flaps and are driven by means of separate flap drive units. In order not to diminish the flight safety in the event of malfunction of a flap drive unit, adjacent flaps are coupled by means of so-called interconnecting struts. Said interconnecting struts are designed such that adjacent flaps carry out different movements within a specific permissible movement range and are able to adopt different positions, for example in order for different adjusting speeds, different dynamic loads, as well as different kinematics of adjacent flaps to be achieved. If, for example, a flap drive unit fails, the flaps are initially still able to be moved within the permissible movement range, depending on the flight situation. This permissible movement range is, in this connection, fixed from an aerodynamic point of view, stalling not being allowed to occur on any of the flaps. If the permissible movement range is exceeded, metal end stops arranged on the interconnecting strut and damping elements damping the displacement movement against these end stops ensure that adjacent flaps are only able to adopt different positions to a limited extent. An exceeding of the movement range may be detected by means of sensors arranged on the interconnecting struts and a corresponding warning signal emitted. The warning signal informs the pilot about the malfunction, whereupon said pilot is no longer allowed to move the flaps. The flap drive units are, therefore, stopped in the respective position and, as a result of which, the flaps are fixed.
An interconnecting strut typically comprises two coaxially arranged strut elements which may be displaced freely relative to one another within a permissible range in the longitudinal direction of the interconnecting strut. The permissible displacement between the strut elements is, in this case, adapted to the permissible movement range between the adjacent flaps. Moreover, the interconnecting strut has end stops defining the displaceability of the strut elements, as well as damping elements damping the impact against the end stops. If the permissible displacement between the two strut elements is exceeded, the displacement movement between the strut elements is damped by the damping elements before reaching the end stops.
In order to damp the displacement movement and, in particular, the impact of the two strut elements against their end stops, for example in the event of a broken connection between the flap drive unit and flap, the damping elements are of multipart construction, made up of a tube and a spherical segment. The tube and the spherical segment are, in this case, coaxially arranged in tandem in the longitudinal direction of the interconnecting strut between the two strut elements. If the permissible displacement between the strut elements is exceeded, the displacement movement is damped. The tube is, in this case, partially plastically and partially elastically expanded by the spherical segment, radially from the inside against the strut element located coaxially on the outside. At the same time, the spherical segment is pressed radially inwardly by the tube against the strut element located coaxially on the inside.
An interconnecting strut is shown by way of example in FIG. 4. The interconnecting strut 100 comprises two coaxially arranged strut elements 200, 210, which may be displaced relative to one another in the longitudinal direction L of the interconnecting strut 100. In order to be able to establish whether the permissible displacement of the two strut elements 200, 210 relative to one another has been exceeded, sensors 400 are arranged on the strut element 200 located coaxially on the outside, which detect the position of a transmitter element 420 connected to the strut element located coaxially on the inside. A damping element 300 is arranged coaxially between the strut elements 200, 210. The damping element 300 of the interconnecting strut 100 shown in FIG. 4 is suitable for damping displacement movements, which are produced both by tensile forces and by compressive forces acting on the interconnecting strut 100. To this end, the damping element 300 consists of a tube 320 and a spherical segment 340 adapted to the diameter of the tube 320. The damping element is arranged between two retaining elements 500, 510. The retaining elements 500, 510 are arranged between two stop surfaces 600, 610 arranged on the strut element 200 located coaxially on the outside. The two retaining elements 500, 510 may be moved towards one another by pressing in the spherical portion 340, on the front face, into the tube 320, on which one respective collar 700, 710 is arranged on both sides of the retaining elements 500, 510 on the strut element 210 located coaxially on the inside. The spacings on both sides between the retaining elements 500, 510 and the collar 700, 710 correspond to the permissible displacement of the two strut elements 200, 210 relative to one another. If the permissible displacement in one of the two directions is exceeded, one respective collar 700, 710 impacts against one of the two retaining elements 500, 510 and moves said retaining elements towards one another by pressing in the spherical segment 340, on the front face, into the tube 320. As a result, the displacement movement between the two strut elements 200, 210 is damped before reaching the end stops.
A drawback with this exemplary interconnecting strut, is firstly the high weight, in particular produced by the high weight of the damping elements, which are to be produced from steel. Moreover, the construction cost for producing the interconnecting strut, in particular for producing the damping elements, is very high as a result of the required choice of material and the accuracy of fit of the spherical segment and tube.